Wideband and ultra-wideband LNAs have received extensive research interests in recent years. A wide range of modern and future communication systems have been proposed that operates over a bandwidth exceeding several GHz, examples of these systems include software-defined radio, ultra-wideband (UWB), and so on. This poses a more stringent requirement on the UWB transceiver, especially for the front-end LNA, which has to provide an ultra-wide bandwidth with reasonable noise figure and impedance matching.
Traditionally, these types of wideband amplifiers were implemented with balanced or distributed architectures that were originally used in microwave circuit design as described in publication “A 0.5-14-GHz 10.6-dB CMOS Cascode Distributed Amplifier”, Liu R. C, et al, 2003 Symposium on VLSI Circuits Digest of Technical Papers. However, large area occupation and high power dissipation of traveling-wave amplifier make it infeasible for low-power single-chip integration. Lumped implementations of UWB LNA were normally achieved by negative feedback or multi-section LC-network. Meanwhile, inductor peaking technique is often adopted for bandwidth enhancement. However, the extra passive devices used for matching purpose increase design complexity and area occupation.
Comparing with narrowband LNA designs, severe tradeoffs between noise figure and source impedance matching exist in wideband LNA. Most of reported UWB LNA designs are focused on bandwidth enhancement. As a result, few of them achieve comparable noise performance. A CMOS UWB LNA employing noise-canceling technique is reported in publication “A broadband noise-canceling CMOS LNA for 3.1-10.6-GHz UWB receiver”, Liao C. H. et al, IEEE 2005 Custom Integrated Circuits Conference where inductive series and shunt peaking techniques are used to extend the effective bandwidth of noise canceling. Another wide-band LNA design exploiting thermal noise canceling technique is reported in publication “Wide-band CMOS Low-Noise Amplifier Exploiting Thermal Noise Canceling”, Federico Bruccoleri et. al, IEEE Journal of Solid-State Circuits, Vol. 39, No. 2, Feb. 2004, where thermal noise of input matching transistor can be sensed and canceled by the feedforward configurations. This avoids the potential instability due to global negative feedbacks. However, the gain performance of such a configuration is often less superior.
There is less freedom in controlling the gain performance of CMOS UWB LNA in prior art devices, especially in the GHz range. Comparing to SiGe BiCMOS where higher gm is available, the gain issue becomes more severe when it is applied to CMOS devices. Therefore, an objective of the present invention is to provide an alternative low noise amplifier with noise cancellation and increased gain thereby advantageously avoids or reduces some of the above-mentioned drawbacks of prior art devices.